Air Conditioner Sizing With Air Handler

[walker]

I'm doing a job for a friend, he has a 1500SqFt (does not include basement) end unit townhouse.  He has a Temp-Mizer HE-52H Air Handler. ( I can't stand these units)  He has plans on finishing the basement.  The Air Handler can handle a 1.5-2Ton.  Should I stick with a 1.5 Ton because these units are notorious for terrible air flow? My buddy is worried that when he finishes the basement the unit wont be able to keep up.  I even spoke with the owner of Temp-Mizer and he stating that the HE-52H doesn't even do 2Ton units, which it clearly states it does in the manual (doesn't even know his own equipment).

What would you guys do, pop in a 1.5 or 2 Ton?

[Admin]

Based on the square footage I would normally go with a 1.5ton, but because you are an end unit you would be safe to go with a 2ton.

I attached a pic of the plans for a 1456sq ft Energy Star townhouse, end unit, with a high velocity heating system, and it calls for a 2ton.

I attached a pic of the manual, and you're right it does say it will work with a 2ton, but the CFM is only around 500.

Don't forget to install an anti ice control (freeze stat) to protect the heating coil from freezing, should the AC coil ice up.

[walker]

Thanks for the info, I'm only hesitant with going with 2 ton because I work on these air handlers all the time and they never seem to get enough air flow for a 2ton, at best they offer 550cfm, and the builder rarely puts enough ducts in for a 2 ton to work properly. But at the same time I don't want to put 1.5 ton in and have it running all the time.

[Admin]

When I install the Lennox 13ACX, 13 seer AC, I use a C33-19, 1.5ton coil, on all my 1.5, 2 and 2.5 ton systems.  This saves me space and money by using the smaller cheaper coil.  This works and is approved but the counter guys will think you're crazy.  Ignore them.

This might be a good option for you.  I'm not sure about other brands but you could install a Lennox 13ACX-24 and a C33-19A coil.  You won't have to worry about only having 500CFM of airflow.

[walker]

I'm putting a GMC VSX13 in. Is that a slab coil? Do you get that coil from lennox parts plus, and how much do they charge for it?
Temp-Mizer wants like over $500 for a 2-ton slab coil!

[Admin]

No, the C33-19 is a standard A Coil.  Lennox sells the Airmax slab coil #MA24-50R410A.  We used this 2ton coil on our 1.5 and 2ton systems.  Now we install our air handlers on a return air plenum so we can use a standard A Coil, to save money.

I would probably go with a 1.5ton if that were my house.  With the proper window coverings the 1.5ton should handle that size home.

In Ottawa where I live, I rather undersize an AC than oversize one.  We don't have long stretches of 30C+ weather.  With a 1.5ton you're friend will appreciate a system that can lower the indoor humidity below 50%.  The 2ton might cool the house down too fast and cycle on and off and never really control the humidity, leaving the friend with a cold damp house.  Plus we aren't 100% sure if the air handler would have enough CFM to work with a 2ton coil.  I think the 1.5ton is the safer bet in your case.

If the basement gets finished and additional supply and return runs are added, I think the overall CFM of the system will increase, and that might increase the chances of being able to use a 2ton coil.  I wouldn't really worry about changing the AC size because of a finished basement though.  It's usually the coldest floor of the house regardless if it's finished or not.

[walker]

Thanks for your insight, I'm going to go with a 1.5 ton.   Never knew you could use an acoil in the return on an air handler, I don't have room in my case I only have about 8 inches to work with.  I'll call LENNOX and see what they charge for slab Coil, hopefully it's much cheaper than temp-mizer